fix: init waits for the iframe to be loaded

jest.config.js

@@ -41,10 +41,10 @@ module.exports = {
   // An object that configures minimum threshold enforcement for coverage results
   coverageThreshold: {
     global: {
-      branches: 89.28,
-      functions: 95.91,
-      lines: 91.32,
-      statements: 91.41,
+      branches: 90.64,
+      functions: 95.95,
+      lines: 93.02,
+      statements: 93.09,
     },
   },
 

src/ledger-iframe-bridge.test.ts

@@ -36,20 +36,6 @@ function isIFrameValid(
   );
 }
 
-/**
- * Simulates the loading of an iframe by calling the onload function.
- *
- * @param iframe - The iframe to simulate the loading of.
- * @returns Returns a promise that resolves when the onload function is called.
- */
-async function simulateIFrameLoad(iframe?: HTMLIFrameElementShim) {
-  if (!isIFrameValid(iframe)) {
-    throw new Error('the iframe is not valid');
-  }
-  // we call manually the onload event to simulate the iframe loading
-  return await iframe.onload();
-}
-
 const LEDGER_IFRAME_ID = 'LEDGER-IFRAME';
 const BRIDGE_URL = 'https://metamask.github.io/eth-ledger-bridge-keyring';
 const INVALID_URL_ERROR = 'bridgeURL is not a valid URL';
@@ -80,7 +66,6 @@ describe('LedgerIframeBridge', function () {
       bridgeUrl: BRIDGE_URL,
     });
     await bridge.init();
-    await simulateIFrameLoad(bridge.iframe);
   });
 
   afterEach(function () {
@@ -123,15 +108,11 @@ describe('LedgerIframeBridge', function () {
   describe('init', function () {
     it('sets up the listener and iframe', async function () {
       bridge = new LedgerIframeBridge();
-
       const addEventListenerSpy = jest.spyOn(global.window, 'addEventListener');
 
       await bridge.init();
 
       expect(addEventListenerSpy).toHaveBeenCalledTimes(1);
-      expect(bridge.iframeLoaded).toBe(false);
-
-      await simulateIFrameLoad(bridge.iframe);
       expect(bridge.iframeLoaded).toBe(true);
     });
   });
@@ -200,8 +181,6 @@ describe('LedgerIframeBridge', function () {
 
   describe('updateTransportMethod', function () {
     it('sends and processes a successful ledger-update-transport message', async function () {
-      bridge.iframeLoaded = true;
-
       const transportType = 'u2f';
 
       stubKeyringIFramePostMessage(bridge, (message) => {
@@ -227,6 +206,14 @@ describe('LedgerIframeBridge', function () {
       expect(bridge.iframe?.contentWindow?.postMessage).toHaveBeenCalled();
     });
 
+    it('throws an error when the bridge is not initialized', async function () {
+      bridge = new LedgerIframeBridge();
+
+      await expect(bridge.updateTransportMethod('u2f')).rejects.toThrow(
+        'The iframe is not loaded yet',
+      );
+    });
+
     it('throws an error when a ledger-update-transport message is not successful', async function () {
       bridge.iframeLoaded = true;
 
@@ -527,7 +514,6 @@ describe('LedgerIframeBridge', function () {
       addEventListenerSpy = jest.spyOn(global.window, 'addEventListener');
       bridge = new LedgerIframeBridge();
       await bridge.init();
-      await simulateIFrameLoad(bridge.iframe);
     });
 
     describe('when configurate bridge url', function () {

src/ledger-iframe-bridge.ts

@@ -110,12 +110,6 @@ export class LedgerIframeBridge
   messageCallbacks: Record<number, (response: IFrameMessageResponse) => void> =
     {};
 
-  delayedPromise?: {
-    resolve: (value: boolean) => void;
-    reject: (error: unknown) => void;
-    transportType: string;
-  };
-
   constructor(
     opts: LedgerIframeBridgeOptions = {
       bridgeUrl: 'https://metamask.github.io/eth-ledger-bridge-keyring',
@@ -128,7 +122,7 @@ export class LedgerIframeBridge
   }
 
   async init() {
-    this.#setupIframe(this.#opts.bridgeUrl);
+    await this.#setupIframe(this.#opts.bridgeUrl);
 
     this.eventListener = this.#eventListener.bind(this, this.#opts.bridgeUrl);
 
@@ -178,12 +172,7 @@ export class LedgerIframeBridge
       // If the iframe isn't loaded yet, let's store the desired transportType value and
       // optimistically return a successful promise
       if (!this.iframeLoaded) {
-        this.delayedPromise = {
-          resolve,
-          reject,
-          transportType,
-        };
-        return;
+        throw new Error('The iframe is not loaded yet');
       }
 
       this.#sendMessage(
@@ -282,28 +271,17 @@ export class LedgerIframeBridge
     });
   }
 
-  #setupIframe(bridgeUrl: string) {
-    this.iframe = document.createElement('iframe');
-    this.iframe.src = bridgeUrl;
-    this.iframe.allow = `hid 'src'`;
-    this.iframe.onload = async () => {
-      // If the ledger live preference was set before the iframe is loaded,
-      // set it after the iframe has loaded
-      this.iframeLoaded = true;
-      if (this.delayedPromise) {
-        try {
-          const result = await this.updateTransportMethod(
-            this.delayedPromise.transportType,
-          );
-          this.delayedPromise.resolve(result);
-        } catch (error) {
-          this.delayedPromise.reject(error);
-        } finally {
-          delete this.delayedPromise;
-        }
-      }
-    };
-    document.head.appendChild(this.iframe);
+  async #setupIframe(bridgeUrl: string): Promise<void> {
+    return new Promise((resolve) => {
+      this.iframe = document.createElement('iframe');
+      this.iframe.src = bridgeUrl;
+      this.iframe.allow = `hid 'src'`;
+      this.iframe.onload = async () => {
+        this.iframeLoaded = true;
+        resolve();
+      };
+      document.head.appendChild(this.iframe);
+    });
   }
 
   #getOrigin(bridgeUrl: string) {

test/document.shim.ts

@@ -1,32 +1,25 @@
 // eslint-disable-next-line import/no-mutable-exports
 let documentShim: any;
 
-try {
-  documentShim = document || {
-    head: {
-      appendChild: () => false,
+const shim = {
+  head: {
+    appendChild: (child: { onload?: () => void }) => {
+      child.onload?.();
     },
-    createElement: () => ({
-      src: false,
-      contentWindow: {
-        postMessage: () => false,
-      },
-    }),
-    addEventListener: () => false,
-  };
-} catch (error) {
-  documentShim = {
-    head: {
-      appendChild: () => false,
+  },
+  createElement: () => ({
+    src: false,
+    contentWindow: {
+      postMessage: () => false,
     },
-    createElement: () => ({
-      src: false,
-      contentWindow: {
-        postMessage: () => false,
-      },
-    }),
-    addEventListener: () => false,
-  };
+  }),
+  addEventListener: () => false,
+};
+
+try {
+  documentShim = document || shim;
+} catch (error) {
+  documentShim = shim;
 }
 
 export default documentShim;